Cancer treatment outcomes have improved over the past 20 years, but treatment decision making in this context remains complex. There are often a number of reasonable treatment alternatives, including no treatment in some circumstances. Patients and doctors often have to weigh up uncertain benefits against uncertain costs. Shared decision making has been espoused as the appropriate model where there is more than one treatment alternative and patient values should determine the optimal choice. Several studies have demonstrated positive outcomes of shared decision making. However, there are a number of barriers to shared decision making, and patients may feel unable to participate. The doctor's willingness and skills in facilitating patient involvement are likely to be critical. A number of interventions have been reported in the literature, but these tend to target either the doctor (communication skills training) or the patient (decision aids, information booklets and question prompt lists). The next generation of interventions will need to target both parties in facilitating a joint approach to decision making.